The present invention relates to electrostatographic printing apparatus and more particularly to a toner recovery device for recovering the residual toner on the latent image carrying member of such apparatus. More specifically, the present invention provides an indication of the quantity of toner recovered in the recovery device preferably with the use of optical sensors.
In an electrostatographic reproducing apparatus commonly in use today, a photoconductive insulating member is typically charged to uniform potential and thereafter exposed to a light image of an original document to be reproduced. The exposure discharges the photoconductive insulating surface in exposed or background areas and creates an electrostatic latent image on the member which corresponds to the image areas contained within the usual document. Subsequently, the electrostatic latent image on the photoconductive insulating surface is made visible by developing the image with developing powder referred to in that art as toner. Most development system employ a developer material which comprises both charged carrier particles and charged toner particles which triboelectrically adhere to the carrier particles. During development the toner particles are attracted from the carrier particles by the charge pattern of the image areas in the photoconductive insualting area to form a powder image on the photoconductive area. This image may subsequently be transferred to a support surface such as copy paper to which it may be permanently affixed by heating or by the application of pressure.
Many commerical applications of the above process employ a modular concept for the various processing stations. For example, the imaging member, developer assembly and cleaner asssembly may be combined in a single unit or cartridge which has a limited life at the end of which it may be discarded and replaced with a new unit or cartridge. Alternatively, a charging device may be added to the unit or the unit may contain either of the developer or the cleaner.